[PATCH v3 2/4] selftests/landlock: Test LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS

[Justin Suess <utilityemal77@gmail.com>]

Check that a successful landlock_restrict_self(2) call with
LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS sets no_new_privs without a prior
prctl(2) call nor CAP_SYS_ADMIN, that a failed call from both an
invalid ruleset and hitting the layer maximum leaves the attribute
unchanged, and that LANDLOCK_RESTRICT_SELF_TSYNC extends it to sibling
threads.  Also check that this flag requires a ruleset, and update the
restrict_self_checks_ordering EPERM checks since this flag is now
checked before the flags validity.

Finally, rename restrict_self_fd_logging_flags to
restrict_self_fd_flags, and restrict_self_logging_flags to
restrict_self_flags to indicate that non-logging flags are now tested.

Update the ABI version and last-flag checks accordingly.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v2->v3:
    - Run clang-format
    - Add max-layers tests (base_test and tsync_test) checking E2BIG and
      that a failed call leaves no_new_privs unchanged
    - Mention the test renames in the commit message
    - Match comment style of surrounding tests

 tools/testing/selftests/landlock/base_test.c  | 99 ++++++++++++++++++-
 tools/testing/selftests/landlock/tsync_test.c | 72 ++++++++++++++
 2 files changed, 166 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index cbd3c1669951..c8ed165a32ed 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -76,7 +76,7 @@ TEST(abi_version)
 	const struct landlock_ruleset_attr ruleset_attr = {
 		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
 	};
-	ASSERT_EQ(10, landlock_create_ruleset(NULL, 0,
+	ASSERT_EQ(11, landlock_create_ruleset(NULL, 0,
 					      LANDLOCK_CREATE_RULESET_VERSION));
 
 	ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
@@ -255,8 +255,15 @@ TEST(restrict_self_checks_ordering)
 
 	/* Checks unprivileged enforcement without no_new_privs. */
 	drop_caps(_metadata);
-	ASSERT_EQ(-1, landlock_restrict_self(-1, -1));
+	ASSERT_EQ(-1, landlock_restrict_self(
+			      -1, ~LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
 	ASSERT_EQ(EPERM, errno);
+	/*
+	 * LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS fulfills the no_new_privs /
+	 * CAP_SYS_ADMIN requirement, so the invalid flags are checked first.
+	 */
+	ASSERT_EQ(-1, landlock_restrict_self(-1, -1));
+	ASSERT_EQ(EINVAL, errno);
 	ASSERT_EQ(-1, landlock_restrict_self(-1, 0));
 	ASSERT_EQ(EPERM, errno);
 	ASSERT_EQ(-1, landlock_restrict_self(ruleset_fd, 0));
@@ -277,6 +284,41 @@ TEST(restrict_self_checks_ordering)
 	ASSERT_EQ(0, close(ruleset_fd));
 }
 
+TEST(restrict_self_max_layers)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_EXECUTE,
+	};
+	struct landlock_path_beneath_attr path_beneath_attr = {
+		.allowed_access = LANDLOCK_ACCESS_FS_EXECUTE,
+		.parent_fd = -1,
+	};
+	const int ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	path_beneath_attr.parent_fd =
+		open("/tmp", O_PATH | O_NOFOLLOW | O_DIRECTORY | O_CLOEXEC);
+	ASSERT_LE(0, path_beneath_attr.parent_fd);
+	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
+				       &path_beneath_attr, 0));
+	ASSERT_EQ(0, close(path_beneath_attr.parent_fd));
+
+	/* Enforces the maximum number of allowed layers. */
+	for (int i = 0; i < LANDLOCK_MAX_NUM_LAYERS; i++)
+		ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
+
+	/* Enforces one too many rulesets. */
+	drop_caps(_metadata);
+	ASSERT_EQ(-1, landlock_restrict_self(
+			      ruleset_fd, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	ASSERT_EQ(E2BIG, errno);
+
+	/* Checks that the failed call did not set no_new_privs. */
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
 TEST(restrict_self_fd)
 {
 	int fd;
@@ -288,7 +330,7 @@ TEST(restrict_self_fd)
 	EXPECT_EQ(EBADFD, errno);
 }
 
-TEST(restrict_self_fd_logging_flags)
+TEST(restrict_self_fd_flags)
 {
 	int fd;
 
@@ -302,11 +344,16 @@ TEST(restrict_self_fd_logging_flags)
 	EXPECT_EQ(-1, landlock_restrict_self(
 			      fd, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF));
 	EXPECT_EQ(EBADFD, errno);
+
+	/* LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS requires a ruleset FD. */
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      fd, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADFD, errno);
 }
 
-TEST(restrict_self_logging_flags)
+TEST(restrict_self_flags)
 {
-	const __u32 last_flag = LANDLOCK_RESTRICT_SELF_TSYNC;
+	const __u32 last_flag = LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS;
 
 	/* Tests invalid flag combinations. */
 
@@ -349,6 +396,17 @@ TEST(restrict_self_logging_flags)
 				      LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON));
 	EXPECT_EQ(EBADF, errno);
 
+	/* LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS requires a ruleset FD. */
+
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      -1, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADF, errno);
+
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      -1, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF |
+					  LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADF, errno);
+
 	/* Tests with an invalid ruleset_fd. */
 
 	EXPECT_EQ(-1, landlock_restrict_self(
@@ -359,6 +417,37 @@ TEST(restrict_self_logging_flags)
 			     -1, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF));
 }
 
+TEST(restrict_self_no_new_privs)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
+	};
+	const int ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+
+	ASSERT_LE(0, ruleset_fd);
+
+	/*
+	 * The calling thread does not need CAP_SYS_ADMIN nor an explicit
+	 * prctl(2) PR_SET_NO_NEW_PRIVS call.
+	 */
+	drop_caps(_metadata);
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	/* Checks that a failed call does not set no_new_privs. */
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      -1, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADF, errno);
+	EXPECT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	/* Checks that a successful call sets no_new_privs. */
+	ASSERT_EQ(0, landlock_restrict_self(
+			     ruleset_fd, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(1, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
 TEST(ruleset_fd_io)
 {
 	struct landlock_ruleset_attr ruleset_attr = {
diff --git a/tools/testing/selftests/landlock/tsync_test.c b/tools/testing/selftests/landlock/tsync_test.c
index 9cf1491bbaaf..afa4a8222248 100644
--- a/tools/testing/selftests/landlock/tsync_test.c
+++ b/tools/testing/selftests/landlock/tsync_test.c
@@ -90,6 +90,78 @@ TEST(multi_threaded_success)
 	EXPECT_EQ(0, close(ruleset_fd));
 }
 
+TEST(multi_threaded_no_new_privs)
+{
+	pthread_t t1, t2;
+	bool no_new_privs1, no_new_privs2;
+	const int ruleset_fd = create_ruleset(_metadata);
+
+	disable_caps(_metadata);
+
+	ASSERT_EQ(0, pthread_create(&t1, NULL, idle, &no_new_privs1));
+	ASSERT_EQ(0, pthread_create(&t2, NULL, idle, &no_new_privs2));
+
+	/* No prior prctl(2) PR_SET_NO_NEW_PRIVS call. */
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	EXPECT_EQ(0, landlock_restrict_self(
+			     ruleset_fd,
+			     LANDLOCK_RESTRICT_SELF_TSYNC |
+				     LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+
+	EXPECT_EQ(1, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	ASSERT_EQ(0, pthread_cancel(t1));
+	ASSERT_EQ(0, pthread_cancel(t2));
+	ASSERT_EQ(0, pthread_join(t1, NULL));
+	ASSERT_EQ(0, pthread_join(t2, NULL));
+
+	/* The no_new_privs flag was enabled on all threads. */
+	EXPECT_TRUE(no_new_privs1);
+	EXPECT_TRUE(no_new_privs2);
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
+TEST(multi_threaded_no_new_privs_max_layers)
+{
+	pthread_t t1, t2;
+	bool no_new_privs1, no_new_privs2;
+	const int ruleset_fd = create_ruleset(_metadata);
+
+	/* Enforces the maximum number of allowed layers. */
+	for (int i = 0; i < LANDLOCK_MAX_NUM_LAYERS; i++)
+		ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
+
+	ASSERT_EQ(0, pthread_create(&t1, NULL, idle, &no_new_privs1));
+	ASSERT_EQ(0, pthread_create(&t2, NULL, idle, &no_new_privs2));
+
+	disable_caps(_metadata);
+
+	/* No prior prctl(2) PR_SET_NO_NEW_PRIVS call. */
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	ASSERT_EQ(-1,
+		  landlock_restrict_self(ruleset_fd,
+					 LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS |
+						 LANDLOCK_RESTRICT_SELF_TSYNC));
+	ASSERT_EQ(E2BIG, errno);
+
+	/* Checks that the failed call did not set no_new_privs. */
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	ASSERT_EQ(0, pthread_cancel(t1));
+	ASSERT_EQ(0, pthread_cancel(t2));
+	ASSERT_EQ(0, pthread_join(t1, NULL));
+	ASSERT_EQ(0, pthread_join(t2, NULL));
+
+	/* The no_new_privs flag was not enabled on any thread. */
+	EXPECT_FALSE(no_new_privs1);
+	EXPECT_FALSE(no_new_privs2);
+
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
 TEST(multi_threaded_success_despite_diverging_domains)
 {
 	pthread_t t1, t2;
-- 
2.54.0